Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Colloidal Quasi-Crystals Discovered

20.01.2011
An international research group led by Professor Stephan Förster of the University of Bayreuth has discovered colloidal quasi-crystals for the first time.

In contrast to the quasi-crystals previously documented, which can only be produced under special laboratory conditions, they are simply structured polymers that evolve through self-assembly.


(A) Defraction image of a colloidal quasi-crystal with 12-fold symmetry; underneath the corresponding tiling. - (B) Defraction image of a colloidal quasi-crystal with 18-fold symmetry; again underneath the corresponding tiling. - The tilings depict the respective complete overall structures. Images: Department of Physical Chemistry, University of Bayreuth; free for publication when references are included.

Due to their structural characteristics, they will probably be used in the development of innovative devices in photonics. In the "Proceedings of the National Academy of Sciences of the United States of America (PNAS)", the participating scientists from Bayreuth, Zurich, Hamburg and Grenoble report this discovery.

Unusual symmetrical structures, made visible in diffraction experiments

Quasi-crystals are characterised by a very unusual alignment of atoms. In normal crystals, atoms form ordered periodical structures; i.e. they arrange themselves into a gap-free integral overall structure, whereby one single symmetrical pattern is regularly repeated. For geometrical reasons, only 1-, 2-, 3-, 4- and 6-fold symmetries are possible. This figure indicates how frequently a structure may be rotated between 0 and 360 degrees, until it is congruent with itself. Quasi-crystals behave differently. They contain ordered aperiodic structures, i.e. there are at least two different symmetrical patterns which form a gap-free integral overall structure, despite not repeating themselves regularly. Under these circumstances, 8-, 10- or 12-fold symmetries may originate.

The structural differences between crystals and quasi-crystals can be made visible in diffraction experiments, using electromagnetic waves. This results in diffraction patterns that provide information on the structure of crystals and quasi-crystals. The discernible symmetrical structures are termed diffraction symmetries.

Colloidal quasi-crystals that evolve through self-assembly

The colloidal quasi-crystals that were discovered are hydrogels (insoluble water-containing polymers). They have a relatively simple structure and evolve by self-assembly of identical "building bricks". Such "building bricks" are polymer micelles: small spherical entities with a diameter ranging between 5 and 100 nanometres, which can be produced on a greater scale without any laboratory input. Therefore colloidal quasi-crystals are easily obtainable to a great number of scientists and to industry.

Professor Stephan Förster's Bayreuth University team has been studying polymer micelles capable of forming lattice structures (i.e. on scales of up to 100 nanometres length) for a considerable period. In joint research projects with the Institute Laue-Langevin in Grenoble and the DESY in Hamburg, it was recently discovered that from such self-assembly, quasi-crystalline lattice structures may evolve. Not only was a 12-fold symmetry observed in diffraction experiments, but also an 18-fold symmetry for the very first time.

Perspectives for innovative uses in photonics

Such experiments are under no circumstances to be considered "glass bead games" of fundamental research. Researchers in the field of photonics, a branch of physics, are interested in high-numbered diffraction symmetries applied to the development of optical technologies for the transfer and saving of information. In recent years it was shown that structures with high diffraction symmetries are characterised by the passage of light rays only in certain directions. They are a particularly suitable medium when it comes to the passage of light rays of a certain wavelength in previously defined directions. Therefore structures with high diffraction symmetries are extremely relevant to the manufacture of photonic devices.

Are the recently discovered hydrogels, with their high diffraction symmetries, suitable as "building materials" for photonics? For this to happen, one obstacle needs to be overcome: photonics requires structural characteristics of several hundred nanometres, while colloidal quasi-crystals do not extend beyond 100 nanometres. Scientists in Bayreuth, Hamburg and Grenoble are currently intensively working on the formation of quasi-crystalline larger structures, suitable for use in photonic devices, from polymer micelles. "I am optimistic that such endeavours will soon be successful", says Professor Stephan Förster.

Quasi-crystals – no longer a laboratory curiosity

Colloidal quasi-crystals are expected to be far more suitable for uses within photonics than the approx. 100 quasi-crystalline compounds known to date. These are nearly all metal alloys that can only be produced in small amounts and under special laboratory conditions. Furthermore, these quasi-crystalline structures range in size between 0.1 and 1 nanometre. For practical use in photonics, they are first and foremost far too small. In order to produce quasi-crystalline structures for photonics, up until now very intricate electrolithographic processes were required. The very existence of quasi-crystals was first proven in 1984 by a research team fronted by the American physicist Dan Shechtman. Afterwards, quasi-crystals were considered a laboratory curiosity for a long period, until photonics researchers were alerted to their unusual structural characteristics.

The international research team now publishing their discovery of colloidal quasi-crystals, includes Stephan Förster and his Bayreuth University team, Professor Walter Steurer and Dr Sofia Deloudi (ETH Zurich), Dr Peter Lindner (ILL Grenoble) and Dr Jan Perlich (DESY Hamburg).

Publication:

Steffen Fischer, Alexander Exner, Kathrin Zielske, Jan Perlich, Sofia Deloudi, Walter Steurer, Peter Lindner, Stephan Förster,
Colloidal quasicrystals with 12-fold and 18-fold diffraction symmetry,
in: Proceedings of the National Academy of Sciences of the United States of America (PNAS),
PNAS published ahead of print January 11, 2011,
DOI-Bookmark: 10.1073/pnas.1008695108
Contact for further information:
Professor Dr. Stephan Förster
Department of Physical Chemistry I
University of Bayreuth D-95440 Bayreuth
Tel: +49 (0)921 / 55–2760
E-Mail (Secr.): elisabeth.duengfelder@uni-bayreuth.de

Christian Wißler | Universität Bayreuth
Further information:
http://www.uni-bayreuth.de

More articles from Physics and Astronomy:

nachricht Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory

nachricht SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>